Archive for November, 2012

Friday Night Update: 5:45pm

Since 2:00pm Wednesday to 4:00pm Friday, 4.00 inches of liquid on Mammoth Pass and still coming down..

Estimated 2.5 to 3.5 feet  on Mammoth Mtn past 24 hours

Snow to taper off this evening with little change in snow level. A 3 more inches possible, except that orographics may contribute to double that over the higher terrain.

Saturday will be interesting. The freezing level is expected to remain pretty much at 9K just like it was today with the snow level about 7500 and heavy snow above 8K.  Tomorrow the freezing level goes up maybe another 100 to 200 feet so not all that sure that precip will go to rain at the village.

The spike to 9700 ft is expected to occur about 4:00am Sunday.  Keep your fingers crossed that micro physical processes come into play and allow the snow to continue falling at the main lodge all day Sunday!  There is a chance….. That would allow several more feet at the main lodge!

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Thursday AM Update:

Just some minor changes mostly in timing and QPF:

By far the biggest impact of this storm for Mono County will be the last in the series of short waves associated with the main “AR” plume into the Central Sierra Sunday morning after daybreak. The air mass will be saturated from top to bottom.

But first of all…..For the Friday/NGT system…..500mb/1000thickness is 552Dm in the Plume which would argue for a snow level 6500 to 7000 feet, however 700mb temps  are about -2.5C in a fairly saturated air-mass. So snow levels will probably be in the 7.2K to 7.5K range Friday/Ngt. Thus it will be all snow up on Mammoth Mtn Friday into Saturday morning…. 1 to 2 feet is expected with this short wave. This is excellent for Canyon lodge!

It is the warmer system late Saturday night into early afternoon Sunday that is of concern as the freezing level goes up by aprox 1000 feet….700mb temps go from -2C Friday to 0c by 4:00am Sunday….while 500/1000 thickness rises to about 562DM or about 100DM rise over Friday.

In a saturated colume, there will be little difference between the Freezing level and the Snow Level. More importantly, CRFC is forecasting 2.5 inches of liquid EQ between 4:00am Sunday and 4:00pm that afternoon near the crest. However, the front/freezing levels should fall rapidly after 2100Z or 1:00pm, thus the vast majority of precip/qpf will occur between 4:00am Sunday and 1:00pm Sunday with a saturated air mass and freezing levels near 10K. Hopefully well get a foot or better at the main lodge during the FROPA Sunday PM before the air mass goes dry!! Over the crest it is possible that rain may briefly go to the top. However, for the most part…its sierra cement Sunday AM over the crest and lots of it!!! This series storms will leave several feet of fresh on Mammoth Mountain…..after it is all said and done!!

Expect somewhat improving weather Monday with the upper jet retreating further to the north Monday through Wednesday next week. However, there is one more shot of moisture that is targeted for mainly Northern Ca Tuesday morning into Wednesday night. Sufficient ridging should cut the Sub Tropical connection by Thursday for California. I think that any precipitation for Mammoth will be over running Tuesday and Wednesday. It should be mainly orographic in nature, so light amounts here in Mammoth with high snow levels. 500mb Heights will rise to 570Dm.  The weekend looks fair for the time being. However a strong Northwest upper jet develops early the following week. That will be a colder pattern with a better potential for snow later that week. (Week 2)

Dr Howard and the Dweebs…………………………..:-)

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All models now in agreement that 3 distinct weather systems will effect the Northern and Central Sierra through Sunday. The first one rolls into the Sierra today about 9:00am. CRFC has 1.50 to 2.25 EQ, between Huntington Lake and Yosemite by about Sunrise Saturday. The precipitation will fall in the form of snow on Mammoth Mountain with the Snow level 7500 to 8000 feet. The Town of Mammoth may pick up between 1 and 3 inches at 8000 feet by this evening. On Mammoth Mountain 3 to 6 inches by this evening……

Thursday will be a day between systems with strong winds developing during the afternoon and the possibility of snow showers. The Dweebs do not expect much in the way of accumulation Thursday, possibly an inch over the upper elevations. There is a high wind watch for Thursday night through Friday for Mono County. Local winds may reach 65mph in gusts!  High temps in the 40s…at 8,000ft.

Storm #2 has precipitation rates increasing by mid-morning friday. The snow level will be about 8000 feet. In the Town of Mammoth….4 to 8 inches of snow may fall at elevations above 8,000 by Saturday Am with 8 to 18 inches over the higher elevations above 9000ft. Strong winds will continue through friday.

With storm #3 approaching….Snow levels will rise all day Saturday and into the night as main Sub-tropical plume moves into the Sierra by late PM.  Any new snowfall in the morning will change to Rain-Snow mix at 8,000 by Noon.  The Snow level will rise to between 8500 and 9,000 feet by Saturday afternoon….then up to *9500 by midnight…..and 10,000+ feet by 4:00am Sunday. Rain will be heavy at times after midnight Saturday.   The heaviest precip rates will occur between 4:00am Sunday and 10:00am Sunday….where an inch plus of rain could fall below 10K. Rainfall over snow pack often times just percolates down through the layers depending upon snow pack densities.

*Note: The Dweebs are using the freezing level as the snow level beginning Midnight Saturday through 10:00AM Sunday as the air-mass is expected to be saturated well beyond 12,000 feet.

Freezing levels and snow levels begin to come down about 10:00am Sunday…..then crash during the afternoon so that by 4:00pm the freezing level is down to 7,000 and a snow level south of 6,000. However, most of the precipitation will be over by then…..

The top of Mammoth Mountain may get a total of 4 to 5 feet of fresh snowfall by Sunday night. It is quite possibly that snowfall accumulations will exceed a foot at the “Main Lodge” between the very late morning Sunday and 4:00pm that afternoon….as freezing levels fall prior to the very end of the storm series…. Although quite a bit if rain may fall at the main lodge, the storm may leave 15 to 20 inches at the main lodge in its wake.

Expect cloudy dry weather Monday through Wednesday with warming temps…..

Long Range Outlook shows the upper ridge that is expected to build over California Monday thru Wednesday mid-week will retrograde over the following weekend to about 140west.  This is going to be either a NW flow pattern or an insider slider pattern depending upon the amplification up stream.  Either way…it will cool down, or get cold and showery with better snow making weather beyond the following weekend….

Dr Howard and the  Dweebs………………………………………..:-)

5:40pm Monday Update:

Confidence increasing for a long duration….high impact precipitation event for the northern and central sierra beginning Wednesday…..

18z GFS is less retrogressive now over the next 6 to 10 days……Stay tuned, we may get some cold air in here yet!!!!

Updates at anytime…..

Pattern changes are underway as more wet and wild weather will return for the high country the 2nd half of this week.  We are now experiencing a weather type more like those back in the early 1980s where by a lot of Subtropical moisture will be entrained into Trofs. However at the moment…..most dynamics are to the north of Mammoth. In the developing weather type, the long wave is both too far west and too far north with retrogression in the cards next week. With the Mother Low Centered about 140west, the upper jet will move on shore over Northern Ca. Before it does, there will be coupling with the Subtropical Jet from time to time for enhancement off-shore.  We here in Mammoth will have to rely a great deal upon the strong onshore flow as well as the natural orographics as a lifting mechanism. There will be plenty of moisture in the clouds but little in the way of upper divergence until a secondary system comes through at the end of the up coming cycle Saturday night into Sunday.  QPF from CRFC has a pretty good bulls-eye over the northern part of the Southern Sierra for a 6 hour period Thursday afternoon. With the amount of heat released through  the conversion process, it suggests snow levels rising up to at least 9K for a time. However, the Dweebs will have to take a good look at the OAK sounding 12z Thursday to see where the 0C line is at saturation and if the saturation is deep enough down to the surface at 7K or 8K for an extended snowfall to the surface. (A case for micro physical processes)

All in all at elevations above McCoy Station, there could be between 3 & 4 feet by Sunday night, taking in considerations for orographics. Questions now arise about what happens beyond next weekend…..

Thoughts:

The warmer waters off the Pacific Coast may be assisting in more ridging over the far west. Blocking from the Dateline north across the North Pole in the Means indicate the Arctic Oscillation is definitely screaming -AO!!!!!..   So why is the far west not stormier with the upper jet coming into Southern Ca? Because too much emphasis is put on the -AO and how all of the WX geeks just wanted the AO to go negative. Well its Negative. Are we waist deep in Snow?  No….   Is the east coast waist deep in Snow? No!  Teleconnections are useful, but they must couple properly with other teleconnections if they are going to be used as biases for predicting climate in various  areas of the World. Yes the -AO is definitely plunging cold air into areas like Europe and the G of AK. But that happened with the Positive phase of the AO last year. So you can get the same results for a different sign!

Odds are as we go toward the middle of December, we will see an increase in the strength of the -NAO. The North Atlantic Oscillation. That will most likely bring Arctic cold to the Mid west and east next month. When both AO and NAO are strongly negative, you can count on the linnier relationship of cold in the east and warmth in the west with confidence. Of course, the PNA will respond strongly positive, especially if the west has warmer then normal SSTAs along the west coast as a support to the teleconnection. I see this in the future probably in later in Dec or January. Our classic Jan thaw while the east freezes!

The Global Wind Oscillation:

Now watch what is happening with the GWO. (Global Wind Oscillation) another interesting issue is that AIM has been on the increase now for the past several weeks. Phase 7-8 (El-Nino like) – the global relative AAM anomaly is positive. Westerly wind anomalies move into the Eastern Hemisphere, broaden in latitudinal extent and link up with deep westerly flow anomalies over the mid-latitude Western Hemisphere. An extended Pacific Ocean jet stream and southward shifted storm track is observed, favoring high impact weather events along the USA west coast. Central Ca to Pacific North west. This is now taking place in California!

Next move: Phase I 

Phase 1 – the global relative AAM tendency is negative. Positive (westerly) AAM anomalies are being removed by surface friction in the Western Hemisphere mid-latitudes and through mountain torques across the Northern Hemisphere topography. The next phase of the oscillation (if it continues) is represented by easterly wind anomalies intensifying over equatorial regions of the Western Hemisphere. This phase has enhanced subtropical jets and closed lows in the subtropics favoring rainfall events over the southwestern USA. Possibly during the 2nd week of Dec for Ca.

SEE: http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

Now see where the MJO goes over the next few weeks. (Phase 1) http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/NCPE_phase_21m_small.gif

The Dweeber………………………………:-)